unmyelinated
Definition
Adjective 1. Lacking a myelin sheath: Describes a nerve fiber (axon) that is not surrounded by a protective, fatty insulating layer called myelin. In the peripheral nervous system, unmyelinated fibers conduct nerve impulses more slowly than myelinated ones.
Usage
The term is primarily used in neurobiology, neurology, and anatomy to describe the physical structure of neurons and nerve fibers. It is a technical, descriptive adjective. - It typically modifies nouns like "axon," "fiber," "nerve," or "neuron." - It is often used in contrast to "myelinated."
Examples
- Scientific Description:
- Pain signals are often transmitted by unmyelinated C fibers.
- The gray matter of the spinal cord contains many unmyelinated axons.
- Comparative Context:
- The conduction velocity in unmyelinated neurons is significantly slower.
Advanced Usage
- "unmyelinated axon": The standard term for a nerve fiber lacking a myelin sheath.
- "unmyelinated nerve fiber": A synonym for an unmyelinated axon.
Variants and Related Words
- Myelinated (adj): The direct antonym; describing a nerve fiber insulated by a myelin sheath.
- Myelinated axons appear white, giving rise to the term "white matter."
- Myelin (n): The fatty insulating substance itself.
- Myelination (n): The process of forming a myelin sheath around an axon.
Synonyms
- Non-myelinated (adj): A less common but equivalent term.
- Amyelinated (adj): A rare synonym with the same meaning.
Antonyms
- Myelinated (adj)
- Medullated (adj): An older, less common term for myelinated.
Adjective
-
(of neurons) not myelinated
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